<div>
    <select id="dino-select">
        <optgroup label="Theropods">
            <option>Tyrannosaurus</option>
            <option selected>Velociraptor</option>
            <option>Deinonychus</option>
        </optgroup>
        <optgroup label="Sauropods">
            <option>Diplodocus</option>
            <option>Saltasaurus</option>
            <option>Apatosaurus</option>
        </optgroup>
    </select>
</div>